1. Field of the Invention
The invention relates to the field of three dimensional surface finishing. More particularly, the invention relates to a flexure and a position monitoring subsystem of a lens preparation system.
2. Prior Art
Ophthalmic and other types of lenses are typically produced from lens blanks of glass or plastic having two major surfaces, one of which is typically finished, and the other of which is unfinished. Cutting, fining and polishing, operations are performed on the unfinished surface of the lens blank by a machine responsive to data corresponding to a particular lens prescription. The cutting operations are usually accomplished by employing a ball mill for plastic lenses, or a grinder for glass lenses. These cutting operations generally create a lens surface closely approximating the shape of the finished lens. However, the cut surface of the lens blank is often rough and requires that subsequent fining and polishing operations be performed on the lens blank to achieve the requisite optical clarity.
The fining and polishing operations are ordinarily performed by engaging the cut surface of the lens blank with a tool having a shape that closely approximates the desired finished shape of the lens as defined by the lens prescription. This abrasive surface is referred to by those skilled in the pertinent art as a tool or "lap". During operation, the lens blank moves relative to the abrasive surface of the lap along a conforming contoured semi-spherical path, thereby fining and/or polishing the lens surface. Laps consist of a mandrel, to which a removable abrasive pad is applied. The lens blank is moved relative to the lap during fining and polishing operations. The combined shape of the mandrel and the pad must conform as closely as possible to the prescribed shape of the lens, therefore, different lens prescriptions require different laps to be used.
Prior lens fining and polishing machines have used mechanical oscillating machines to move the lap relative to the lens blank. The oscillating motions have been fixed, defined by the mechanical structure of the fining and polishing machine, with differences between the ideal motion for sliding the lap against the lens blank taken up by a biasing mechanism which provides the force between the lap and lens blank and by leaving either the lap or lens blank free to pivot about at least one axis in response to the motion of the fining and polishing machine.